This section provides background information related to the present disclosure which is not necessarily prior art.
Cooling systems, refrigeration systems, heat-pump systems, and other climate-control systems include a fluid circuit having a condenser, an evaporator, an expansion device disposed between the condenser and evaporator, and a compressor circulating a working fluid (e.g., refrigerant) between the condenser and the evaporator. The compressor may be one of any number of different compressors. For example, the compressor may be a scroll compressor or a reciprocating compressor that selectively circulates the working fluid among the various components of a cooling, refrigeration, or heat-pump system. Regardless of the particular type of compressor employed, consistent and reliable operation of the compressor is required to ensure that the cooling, refrigeration, or heat-pump system in which the compressor is installed is capable of consistently and reliably providing a cooling and/or heating effect on demand.
Compressors typically include a hermetic or semi-hermetic shell. A partition disposed within the shell divides the shell into a suction-pressure zone and a discharge-pressure zone. The working fluid is drawn into the suction-pressure zone and compressed by a compression mechanism and discharged therefrom into the discharge-pressure zone.
A lubricant sump may be disposed within the shell and stores a volume of lubricant, such as oil, for example. The lubricant serves to lubricate the moving components of the compressor and can flow with the working fluid through the compression mechanism and into the discharge-pressure zone of the compressor. The temperature of the lubricant and working fluid in the discharge-pressure zone is elevated relative to the lubricant and working fluid in the suction-pressure zone.
In the discharge-pressure zone, some or all of the lubricant is separated from the working fluid and returned to the lubricant sump. The lubricant is subsequently recycled through the compressor and may interact with the working fluid being drawn in the suction-pressure zone of the compressor. The elevated temperature of the lubricant raises the temperature of the working fluid in the suction-pressure zone, thereby increasing the superheat of the working fluid and reducing the volumetric efficiency of the compressor. Accordingly, it may be desirable to restrict an amount of lubricant flow through the compressor to minimize heating of the working fluid in the suction-pressure zone, while maintaining sufficient lubrication of the moving components of the compressor.